Sheet processing apparatus, method for using the same image and image forming system

ABSTRACT

A sheet processing apparatus for receiving and processing a sheet conveyed from an image forming apparatus, the sheet processing apparatus comprising: a discharging unit configured to discharge the sheet; a stacking unit configured to stack thereon the sheet discharged by the discharging unit; a blowing air unit configured to blow air along a direction parallel to a surface of the sheet being stacked; a first alignment unit having a pair of alignment plane opposed each other, the first alignment unit configured to align the sheet in a direction parallel to a discharging direction of the sheet; and a second alignment unit configured to align the sheet in a direction orthogonal to the discharging direction of the sheet, wherein the blowing air unit is provided at a position opposed to the alignment plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2012-195364 filed in Japan on Sep. 5, 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet processing apparatus, an image forming system, and a sheet processing method. More particularly, the invention relates to a sheet processing apparatus that blows air when discharging a conveyed sheet recording medium (simply referred to as a “sheet” in the present specification), such as a paper sheet, a recording sheet, a transfer sheet, and a viewgraph used for an overhead projector (OHP), thereby aligning the sheet, an image forming system including the sheet processing apparatus and an image forming apparatus, such as a copier, a printer, a facsimile, and a digital multifunction peripheral (MFP), and a sheet processing method performed by the sheet processing apparatus.

2. Description of the Related Art

Conventionally widely known and used are sheet processing apparatuses that perform various types of processing, such as post-processing including alignment, stapling, folding, and binding, on sheets discharged from an image forming apparatus. Such sheet processing apparatuses that perform post-processing are herein referred to as sheet post-processing apparatuses.

Japanese Patent Application Laid-open No. 2003-252520, for example, discloses such a sheet post-processing apparatus. It is an object of the invention to provide a sheet post-processing apparatus that performs binding on sheets received from a Z-folding device and reliably conveys and discharges the sheets without causing buckling, wrinkle, breakage, or the like.

The sheet post-processing apparatus performs Z-folding on sheets discharged from an image forming apparatus and places the sheets on a sheet placing table. The sheet post-processing apparatus then aligns and binds the sheets and discharges the sheet bundle thus bound with a discharging belt and a pair of ejecting rollers of a discharging unit. To achieve the object described above, the sheet post-processing apparatus includes a control unit that performs the following control. The trailing end of the sheet bundle in a discharging direction is held by the discharging belt of the discharging unit and is conveyed on the sheet placing table with the pair of ejecting rollers half-opened. After the leading end of the sheet bundle in the discharging direction reaches the vicinity of a holding position of the pair of ejecting rollers, the conveyance of the sheet bundle is temporarily stopped. Subsequently, the pair of ejecting rollers is pressed against each other to re-convey the sheet bundle while pressing and sandwiching the sheet bundle, thereby discharging the sheet bundle to the outside of the apparatus.

In the invention, the sheet post-processing apparatus is provided with a blowing unit above the sheet placing table. When the Z-folded sheet is placed onto the sheet placing table, the blowing unit is caused to operate to align the Z-folded sheet by pressing the back surface of the sheet against the sheet placing table with blown air. The blowing unit is arranged near the center of the length of the Z-folded sheet placed on the sheet placing table in a conveying direction and near the center of the Z-fold sheet in a width direction orthogonal to the conveying direction.

In the invention disclosed in Japanese Patent Application Laid-open No. 2003-252520, the sheet post-processing apparatus is provided with the blowing unit above the sheet placing table. The sheet post-processing apparatus holds down a folded sheet by causing the blowing unit to blow air to the back surface of the sheet, thereby preventing buckling, wrinkle, breakage, or the like. The sheet post-processing apparatus, however, does not consider poor alignment caused by sheets, such as coated papers, sticking to each other, for example. In terms of unfolded sheets, blowing air from the blowing unit arranged above the sheet placing table to the back surface of the sheets is ineffective for preventing the sheets from sticking to each other. As a result, the sheet post-processing apparatus fails to ensure excellent alignment of the sheets sticking to each other.

It is an object of the present invention to prevent sheets from sticking to each other and ensure excellent alignment accuracy.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve the problems in the conventional technology.

According to an aspect of the invention, a sheet processing apparatus for receiving and processing a sheet conveyed from an image forming apparatus is provided. The sheet processing apparatus includes: a discharging unit configured to discharge the sheet; a stacking unit configured to stack thereon the sheet discharged by the discharging unit; a blowing air unit configured to blow air along a direction parallel to a surface of the sheet being stacked; a first alignment unit having a pair of alignment plane opposed each other, the first alignment unit configured to align the sheet in a direction parallel to a discharging direction of the sheet; and a second alignment unit configured to align the sheet in a direction orthogonal to the discharging direction of the sheet, wherein the blowing air unit is provided at a position opposed to the alignment plane.

According to another aspect of the invention, a method for using the sheet processing apparatus is provided. The method includes: by the discharging unit, discharging the sheet; by the stacking unit, stacking thereon the sheet discharged by the discharging unit; by the blowing air unit, blowing air along the direction parallel to the surface of the sheet being stacked; by the first alignment unit having a pair of alignment plane opposed each other, the first alignment unit configured to align the sheet in a direction parallel to a discharging direction of the sheet; and a second alignment unit configured to align the sheet in a direction orthogonal to the discharging direction of the sheet, wherein the blowing unit is provided at a position opposed to the alignment plane.

According to further aspect of the invention, an image forming system is provided. The image forming system includes: the sheet processing apparatus set forth in claim 1; and the image forming apparatus.

The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a system configuration of an image forming system according to an embodiment of the present invention;

FIG. 2 is a schematic of a configuration of an edge binding tray in FIG. 1 viewed from the stacking surface side of the tray;

FIG. 3 is a front view illustrating a main section of a schematic configuration of a lower part of the edge binding tray;

FIG. 4 is a perspective view of a schematic configuration of the edge binding tray and an accessory mechanism thereof;

FIG. 5 is a side view illustrating an operation of a releasing belt in FIG. 1;

FIGS. 6A and 6B are views for explaining an operation performed by a staple unit, illustrating a state in which a first sheet is conveyed;

FIGS. 7A and 7B are views for explaining an operation performed by the staple unit, illustrating a state in which the first sheet is discharged onto the edge binding tray by a pair of staple ejecting rollers;

FIGS. 8A and 8B are views for explaining an operation performed by the staple unit, illustrating a state in which conveyance of the first sheet to the edge binding tray is completed;

FIGS. 9A and 9B are views for explaining an operation performed by the staple unit, illustrating a state in which a second sheet is discharged onto the first sheet;

FIGS. 10A and 10B are views for explaining an operation performed by the staple unit, illustrating a state in which discharge of a plurality of sheets onto the edge binding tray is completed;

FIG. 11 is a block diagram of a control configuration of the image forming system formed of a sheet post-processing apparatus and an image forming apparatus;

FIG. 12 is a flowchart of a process of blowing operation control;

FIG. 13 is a front view of a selection screen used for selecting a blowing mode on an operation panel of the image forming apparatus; and

FIG. 14 is a front view of a setting screen used for setting a blowing air volume on the operation panel of the image forming apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an aligning unit that performs alignment in a sheet width direction with a blowing unit to align sheets on a staple tray. The blowing unit blows air toward the center of the sheets in a conveyance direction from both sides of the sheets. This makes it possible to align the sheets while preventing the sheets from sticking to each other. Exemplary embodiments according to the present invention are described below with reference to the accompanying drawings.

FIG. 1 is a schematic of a system configuration of an image forming system formed of a sheet post-processing apparatus serving as a sheet processing apparatus according to an embodiment of the present invention, and an image forming apparatus.

In FIG. 1, an image forming apparatus PR includes at least an image processing circuit, an optical writing device, a developing device, a transfer device, and a fixing device. The image processing circuit converts received image data into image data in a printable format. The optical writing device performs optical wiring on a photosensitive element based on an image signal output from the image processing circuit. The developing device develops a latent image formed on the photosensitive element by the optical writing into a toner image. The transfer device transfers the toner image developed by the developing device onto a sheet. The fixing device fixes the toner image thus transferred to the sheet. The image forming apparatus PR feeds the sheet to which the toner image is fixed to a sheet post-processing apparatus PD. The sheet post-processing apparatus PD performs desired post-processing. While the image forming apparatus PR is an electrophotography image forming apparatus as described above, all publicly known image forming apparatuses, such as an inkjet image forming apparatus and a thermal-transfer image forming apparatus, can be used. In the present embodiment, the image processing circuit, the optical writing device, the developing device, the transfer device, and the fixing device correspond to an image forming unit.

The sheet post-processing apparatus PD is attached to the side surface of the image forming apparatus PR. A sheet discharged from the image forming apparatus PR is guided into the sheet post-processing apparatus PD. The sheet post-processing apparatus PD includes a conveying path A, a conveying path B, a conveying path C, a conveying path D, and a conveying path H. The sheet is first conveyed into the conveying path A including a post-processing unit (a punch unit 50 serving as a perforating unit in the present embodiment) that performs post-processing on one sheet.

The conveying path B guides the sheet passing through the conveying path A to an upper tray 201, whereas the conveying path C guides the sheet to a shift tray 202. The conveying path D guides the sheet to a processing tray F (hereinafter, also referred to as an “edge binding tray”) that performs alignment and staple binding, for example. The sheet is distributed from the conveying path A to any one of the conveying paths B, C, and D by a bifurcating claw 15 and a bifurcating claw 16.

The sheet post-processing apparatus can perform various types of processing on a sheet, such as punching (by a punch unit 50), sheet alignment and edge binding (by a jogger fence 53 and an edge binding stapler S1), sheet alignment and saddle-stitch binding (by a saddle-stitch upper jogger fence 250 a, a saddle-stitch lower jogger fence 250 b, and a saddle-stitch stapler S2), sheet-sorting (by the shift tray 202), and center-folding (by a folding plate 74 and folding rollers 81). To perform the processing described above, the sheet is selectively conveyed from the conveying path A to any one of the conveying paths B, C, and D each connected thereto. The conveying path D includes a sheet containing unit E. The edge binding tray F, a saddle-stitching and center-folding tray G, and the discharge conveying path H are provided on the downstream of the conveying path D.

The conveying path A is positioned on the upstream of the conveying path B, the conveying path C, and the conveying path D, and is commonly connected to the conveying paths B, C, and D. The conveying path A is provided with an entrance sensor 301 that detects a sheet received from the image forming apparatus PR, an entrance roller 1, the punch unit 50, a chad hopper 61, a pair of carriage rollers 2, the first bifurcating claw 15, and the second bifurcating claw 16 in this order from the upstream side. The first bifurcating claw 15 and the second bifurcating claw 16 are maintained in the state illustrated in FIG. 1 (an initial state) by a spring, which is not illustrated. Turning-ON a first solenoid and a second solenoid, neither of which is illustrated, drives the bifurcating claws 15 and 16, respectively. Switching ON and OFF the first solenoid and the second solenoid, respectively, changes the combination of bifurcating directions of the first bifurcating claw 15 and the second bifurcating claw 16. Thus, the sheet is distributed to any one of the conveying paths B, C, and D.

To guide a sheet into the conveying path B, the state of the first bifurcating claw 15 remains the state of FIG. 1, that is, the first solenoid remains in the OFF state (the first bifurcating claw 15 is directed downward in the initial state). Thus, the sheet is conveyed thorough a carriage roller 3 and a discharging roller 4 and discharged onto the upper tray 201. To guide the sheet into the conveying path C, the first and the second solenoids are turned ON in the state of FIG. 1 (the second bifurcating claw 16 is directed upward in the initial state). This causes the bifurcating claw 15 to rotate upward and causes the bifurcating claw 16 to rotate downward. Thus, the sheet is conveyed thorough a pair of carriage rollers 5 and a pair of ejecting rollers 6 (6 a and 6 b) to the shift tray 202. In this case, sheet-sorting is performed by a shift tray discharging unit positioned at the most-downstream part of the sheet post-processing unit PD. Sheet-sorting is performed by the pair of ejecting rollers 6 (6 a and 6 b), a returning roller 13, a sheet surface detecting sensor 330, the shift tray 202, and a shift mechanism and a shift tray lifting mechanism, neither of the mechanisms is illustrated. The shift mechanism reciprocates the shift tray 202 in a direction orthogonal to a sheet conveying direction. The shift tray lifting mechanism lifts the shift tray 202 up and down.

To guide the sheet into the conveying path D, the first solenoid that drives the first bifurcating claw 15 is turned ON, and the second solenoid that drives the second bifurcating claw is turned OFF. This causes the bifurcating claw 15 and the bifurcating claw 16 to rotate upward. Thus, the sheet is conveyed thorough the pair of carriage rollers 2 and a pair of carriage rollers 7 to the conveying path D. The sheet guided into the conveying path D is conveyed to the edge binding tray F and is aligned and stapled on the edge binding tray F, for example. The sheet is distributed to one of the conveying path C leading to the shift tray 202 and the saddle-stitching and center-folding tray G (hereinafter, also simply referred to as a “saddle-stitching tray”) that performs folding and other processing by a sheet guiding member 44.

When the shift tray 202 is selected, a sheet bundle PB is discharged onto the shift tray 202 by the pair of ejecting rollers 6. By contrast, a sheet bundle PB conveyed to the saddle-stitching tray G is folded and saddle-stitched on the saddle-stitching tray G. The sheet bundle PB is then conveyed through the discharge conveying path H and discharged onto a lower tray 203 by discharging rollers 83.

A bifurcating claw 17 is arranged in the conveying path D and is maintained in the state illustrated in FIG. 1 by a low-load spring, which is not illustrated. After a sheet is conveyed by the pair of carriage rollers 7 and the trailing end of the sheet passes by the bifurcating claw 17, at least a pair of carriage rollers 9 is rotated backward among the pair of carriage rollers 9, a pair of carriage rollers 10, and a pair of staple ejecting rollers 11. This enables the sheet to move backward along a turn guide 8. The sheet is guided into the sheet containing unit E from the trailing end thereof and retained (pre-stacked) in the sheet containing unit E. Thus, the sheet can be conveyed with a subsequent sheet stacked thereon. Repeating this operation makes it possible to convey the sheet together with one or more sheet(s) stacked thereon. A reference numeral 304 denotes a pre-stack sensor used for setting a reverse conveyance timing for pre-stacking the sheet.

To guide sheets into the conveying path D and perform sheet alignment and edge binding thereon, the sheets are conveyed to the edge binding tray F by the pair of staple ejecting rollers 11 and sequentially stacked on the edge binding tray F. At this time, a tapping roller 12 taps to slide each sheet in an arrow D1′ direction, thereby aligning the sheets in the longitudinal direction (the sheet conveying (discharging) direction or an arrow D1 direction). The jogger fence 53 aligns the sheets in a direction orthogonal to the sheet conveying direction (also referred to as a sheet width direction (arrow D2 direction)). At an interval between jobs, that is, a time period from when the last sheet of the sheet bundle PB is conveyed and to when the first sheet of a subsequent sheet bundle PB is conveyed, the edge-binding stapler S1 serving as a binding unit is driven to perform binding by a staple signal supplied from a central processing unit (CPU) 101, which will be described later. The sheet bundle PB thus bound is promptly conveyed to the pair of ejecting rollers 6 by a releasing belt 52 (refer to FIG. 2) provided with a releasing claw 52 a protruding therefrom. The sheet bundle PB is then discharged onto the shift tray 202 set at a reception position.

As illustrated in FIG. 1, the edge binding stapler S1 is formed of a stitcher (driver) S1a that discharges a staple and a clincher S1b that bends the tip of the staple. A space S1c is formed between the stitcher S1a and the clincher S1b so as to allow a first trailing-end reference fence 51 a and a second trailing-end reference fence 51 b to pass therethrough. This configuration enables the edge binding stapler S1 to move without interfering with the trailing-end reference fence 51. The edge binding stapler S1 is formed of the stitcher S1a and the clincher S1b configured integrally, unlike the saddle-stitch stapler S2.

The stitcher S1a functions as a fixed part that does not move in a vertical direction with respect to the sheet surface. The clincher S1b functions as a moving part that moves in the vertical direction with respect to the sheet surface. To perform a binding operation on the sheet bundle PB, the clincher S1b moves toward the stitcher S1a at a predetermined portion to be bound of the sheet bundle PB coming into contact with stack surfaces 51 a 1 and 51 b 1 (refer to FIG. 4) of the first trailing-end reference fence 51 a and the second trailing-end reference fence 51 b, respectively. Thus, the binding operation is performed.

As illustrated in FIG. 2 and FIG. 5, the releasing belt 52 is positioned at the center of alignment in the sheet width direction. The releasing belt 52 is stretched around pulleys 62 and driven by a releasing belt driving motor 157. A plurality of releasing rollers 56 are arranged symmetrically with respect to the releasing belt 52. The releasing rollers 56 are provided in a manner rotatable with respect to a driving shaft and function as driven rollers. FIG. 5 is a perspective view illustrating an operation of the releasing belt in FIG. 1. The arrow D1 direction corresponds to the sheet conveying direction.

The home position of the releasing claw 52 a is detected by a releasing belt HP sensor 311. The releasing belt HP sensor 311 is turned ON and OFF by the releasing claw 52 a provided to the releasing belt 52. Two releasing claws 52 a are arranged at positions opposite to each other on the outer circumference of the releasing belt 52. The two releasing claws 52 a alternately convey the sheet bundle PB accommodated in the edge binding tray F. In addition, the releasing belt 52 can be rotated backward as needed. This enables the leading end of the sheet bundle PB accommodated in the edge binding tray F in the conveying direction to be aligned by the back surface of the second releasing claw 52 a opposite to the first releasing claw 52 a waiting to move the sheet bundle PB.

In FIG. 1, a reference numeral 98 denotes a pressing member (a trailing-end pressing lever). The trailing-end pressing member 98 is positioned at the lower end of the trailing-end reference fence 51 so as to press the trailing end of the sheet bundle PB accommodated in the trailing-end reference fence 51. The trailing-end pressing member 98 reciprocates in a direction approximately vertical to the edge binding tray F. The sheets discharged onto the edge binding tray F are aligned one by one in the longitudinal direction (sheet conveying direction) by the tapping roller 12. If the sheets stacked on the edge binding tray F have a curl at the trailing end thereof or are soft sheets, the trailing end of the sheets tends to buckle and bulge by their own weight. As the number of stacked sheets increases, a space for a subsequent sheet in the trailing-end reference fence 51 decreases. This may possibly lead to poor alignment in the longitudinal direction.

To reduce the bulge at the trailing end of the sheets so as to facilitate the sheet's entering the trailing-end reference fence 51, a pressing mechanism that presses the trailing end of the sheets is provided. The pressing member 98 directly presses the sheet or the sheet bundle PB. The pressing member is also referred to as a pressing lever.

Reference numerals 302, 303, 304, 305, and 310 in FIG. 1 denote sheet detecting sensors. The sheet detecting sensors 302, 303, 304, 305, and 310 detect whether a sheet passes or whether a sheet is stacked at the positions where the respective sheet detecting sensors are provided.

While a large area is denoted by the reference numeral F as the edge binding tray in FIG. 1, the reference numeral F specifically represents the tray on which a sheet P is discharged by the pair of staple ejecting rollers 11, aligned, stacked, and bound. The sheet P collectively represents a first sheet P1, a second sheet P2, an n−1-th sheet Pn−1, and an n-th sheet Pn, which will be described later.

FIG. 2 is a schematic of a configuration of the edge binding tray F viewed from the stacking surface side of the tray. FIG. 2 corresponds to a schematic viewed from the right surface in FIG. 1. In FIG. 2, jogger fences 53 a and 53 b align, in the width direction, the sheets received from the image forming apparatus PR positioned on the upstream thereof. The sheets are caused to abut on the first trailing-end reference fence 51 a and the second trailing-end reference fence 51 b (denoted by the reference numeral 51 in FIG. 1) and be aligned in the longitudinal direction.

The jogger fences 53 a and 53 b are provided with blowing devices 54 a and 54 b that blow air toward the inside of the jogger fences 53 a and 53 b, respectively. The blowing devices 54 a and 54 b can be moved within a preset range in the longitudinal direction of the jogger fences 53 a and 53 b (an arrow D3 direction), respectively, by a moving mechanism, which is not illustrated. A publicly known mechanism is used as the moving mechanism, including a timing belt and a conveying screw.

The blowing devices 54 a and 54 b have blowing ports 54 a 1 and 54 b 1 open to the inside of the jogger fences 53 a and 53 b, respectively. Air is blown from the blowing ports 54 a 1 and 54 b 1 to the inside of the jogger fences 53 a and 53 b. The blowing ports 54 a 1 and 54 b 1 are provided with a louver together with an angle changing mechanism of the louver, which are not illustrated. The angle changing mechanism can change blowing directions 54 a 2 and 54 b 2 to respective arrow D4 directions, for example. The maximum angle of the change is set to 90 degrees in the present embodiment, for example.

While the blowing angle is rotated only to a sheet discharging direction in FIG. 2, the blowing angle may be rotated in a direction opposite to the sheet discharging direction. The blowing angle is set appropriately depending on the sheet size and the positions of the blowing ports 54 a 1 and 54 b 1. A publicly known mechanism is used as the angle changing mechanism of the louver, including a mechanism that is provided with a sliding member connected to the louver and rotates each blade of the louver about a rotation fulcrum. The sliding member is driven by a motor.

In the present embodiment, the blowing devices 54 a and 54 b are directly provided to the jogger fences 53 a and 53 b, respectively. Alternatively, a blowing source including a fan and a fan motor may be separately provided, for example. The blowing source sends air to the blowing ports 54 a 1 and 54 b 1 via an extensible hose duct such that the air is blown through the blowing ports 54 a 1 and 54 b 1.

FIG. 3 is a front view illustrating a main section of a schematic configuration of a lower part of the edge binding tray F. The trailing-end reference fence 51, the edge binding stapler S1, and the pair of staple ejecting rollers 11 are provided to the lower part of the edge binding tray F. The pressing member 98 is arranged in a manner facing the trailing-end reference fence 51. As described above, the pressing member 98 presses the trailing end of the sheet bundle PB accommodated in the trailing-end reference fence 51. The pressing member 98 is positioned at the lower end of the trailing-end reference fence 51 and can reciprocate in a direction approximately vertical to the edge binding tray F. The pressing member 98 is provided in plurality (three in the present embodiment) in the sheet width direction. The respective pressing members 98 are moved in the sheet width direction in association with the edge binding stapler S1 by a mechanism, which will be described later. The pressing members 98 can come close to and move away from the sheet bundle, thereby pressing the trailing end of the sheet bundle at a predetermined pressure. In a binding operation, the pressing members 98 hold the sheet bundle between the trailing-end reference fences 51.

FIG. 4 is a perspective view of a schematic configuration of the edge binding tray F and an accessory mechanism thereof. As illustrated in FIG. 4, the sheets guided to the edge binding tray F by the pair of staple ejecting rollers 11 are sequentially stacked on the edge binding tray F. If the number of sheets discharged onto the edge binding tray F is one, the tapping roller 12 aligns the sheet in the longitudinal direction (sheet conveying direction), and the jogger fences 53 a and 53 b aligns the sheet in the width direction (direction orthogonal to the sheet conveying direction). The tapping roller 12 is caused to swing like a pendulum about a fulcrum 12 a by a tapping solenoid 170. The tapping roller 12 intermittently acts on the sheet conveyed to the edge binding tray F to move the sheet in the arrow D1′ direction, thereby causing a sheet trailing end ST to abut on the trailing-end reference fence 51. The tapping roller 12 rotates in the counterclockwise direction. As illustrated in FIG. 2 and FIG. 4, the jogger fence 53 is formed in pairs arranged on the front side and the rear side (53 a and 53 b, which are on the left side and the right side in FIG. 2 and FIG. 4). The jogger fence 53 is driven to reciprocate in the sheet width direction via a timing belt by a jogger motor 158 that can rotate forwardly and reversely.

After the alignment operation is completed, the edge binding stapler S1 performs binding. Subsequently, as is clear from a perspective view illustrating an operation of the releasing belt of FIG. 5, the releasing belt 52 is driven to rotate in the counterclockwise direction by the releasing belt driving motor 157. Thus, the sheet bundle PB thus bound is lifted by the releasing claw 52 a provided to the releasing belt 52 and is released from the edge binding tray F.

Reference numerals 64 a and 64 b denote a front side plate and a rear side plate, respectively. The same operation as described above can be performed on a sheet bundle not to be bound after the alignment.

A sheet bundle deflecting mechanism I is provided on the downstream of the edge binding tray F in the sheet conveying direction. As illustrated in FIG. 1, the conveying path that conveys the sheet bundle PB from the edge binding tray F to the saddle-stitching tray G and from the edge binding tray F to the shift tray 202 and a conveying unit that conveys the sheet bundle PB are formed of a conveying mechanism 35, the releasing roller 56, and the guiding member 44. The conveying mechanism 35 applies a conveying force to the sheet bundle PB. The releasing roller 56 causes the sheet bundle PB to turn. The guiding member 44 guides the sheet bundle PB to turn.

Specifically, a driving force of a driving shaft 37 is transmitted to a roller 36 of the conveying mechanism 35 via a timing belt. The roller 36 is connected to the driving shaft 37 by an arm and can swing about the driving shaft 37 serving as a rotation fulcrum. The roller 36 of the conveying mechanism 35 is driven to swing by a cam 40. The cam 40 is driven to rotate about a rotating shaft by a motor, which is not illustrated. In the conveying mechanism 35, a driven roller 42 is arranged at a position opposite to the roller 36. The driven roller 42 and the roller 36 sandwich the sheet bundle PB, and an elastic material applies a pressure to the sheet bundle PB. Thus, the conveying mechanism 35 applies a conveying force to the sheet bundle PB.

The conveying path that causes the sheet bundle PB to turn from the edge binding tray F to the saddle-stitching tray G is formed between the releasing roller 56 and the inner surface of the guiding member 44 facing the releasing roller 56. The guiding member 44 is driven to rotate about a fulcrum by a bundle bifurcation driving motor 161 (refer to FIG. 2). To convey the sheet bundle from the edge binding tray F to the shift tray 202, the guiding member 44 rotates in the clockwise direction in FIG. 1 about the fulcrum. As a result, a space between the outer surface of the guiding member 44 (surface not facing the releasing roller 56) and a guide plate arranged above the outer surface functions as the conveying path.

To convey the sheet bundle PB from the edge binding tray F to the saddle-stitching tray G, the trailing end of the sheet bundle PB aligned on the edge binding tray F is lifted by the releasing claw 52 a. The roller 36 of the conveying mechanism 35 and the driven roller 42 facing the roller 36 sandwich the sheet bundle and apply a conveying force to the sheet bundle. At this time, the roller 36 of the conveying mechanism 35 stands by at a position where the roller 36 does not come into contact with the leading end of the sheet bundle PB. After the leading end of the sheet bundle PB passes by, the roller 36 of the conveying mechanism 35 is brought into contact with the surface of the sheet to apply a conveying force to the sheet bundle PB. At this time, the guiding member 44 and the releasing roller 56 form a guide of the turn conveying path, thereby conveying the sheet bundle PB to the saddle-stitching tray G on the downstream thereof.

As illustrated in FIG. 1, the saddle-stitching tray G is provided on the downstream of the sheet bundle deflecting mechanism formed of the conveying mechanism 35, the guiding member 44, and the releasing roller 56. The saddle-stitching tray G is provided nearly vertically on the downstream of the sheet bundle deflecting mechanism. The saddle-stitching tray G includes a saddle-stitching mechanism arranged at the center thereof, an upper bundle feed guiding plate 92 arranged above the folding mechanism, and a lower bundle feed guiding plate 91 arranged below the folding mechanism.

The upper bundle feed guiding plate 92 is provided with an upper bundle carriage roller 71 in an upper part thereof and a lower bundle carriage roller 72 in a lower part thereof. A saddle-stitch upper jogger fence 250 a is arranged on both sides of the upper bundle feed guiding plate 92 along the side surfaces thereof so as to cover the space between the rollers 71 and 72. Similarly, a saddle-stitch lower jogger fence 250 b is provided on both sides of the lower bundle feed guiding plate 91 along the side surfaces thereof. The saddle-stitch stapler S2 is arranged at the position where the saddle-stitch lower jogger fence 250 b is provided.

The saddle-stitch upper jogger fence 250 a and the saddle-stitch lower jogger fence 250 b are driven by a driving mechanism, which is not illustrated. The saddle-stitch upper jogger fence 250 a and the saddle-stitch lower jogger fence 250 b perform an alignment operation in a direction (sheet width direction) orthogonal to the sheet conveying direction. Two saddle-stitch staplers S2 each formed of a pair of a clincher and a driver are provided with a predetermined gap interposed therebetween in the sheet width direction.

A movable trailing-end reference fence 73 is arranged in a manner traversing the lower bundle feed guiding plate 91. The movable trailing-end reference fence 73 can be moved in the sheet conveying direction (vertical direction in FIG. 1) by a moving mechanism including a timing belt and a driving mechanism. As illustrated in FIG. 1, the driving mechanism is formed of a driving pulley and a driven pulley around which the timing belt is stretched and a stepping motor that drives the driving pulley. A trailing-end tapping claw 251 and a driving mechanism thereof are provided to an upper end of the upper bundle feed guiding plate 92. The trailing-end tapping claw 251 can be reciprocated by a timing belt 252 and a driving mechanism, which is not illustrated, in a direction away from the sheet bundle deflecting mechanism and a direction for pressing the trailing end of the sheet bundle (corresponding to the trailing end when the sheet bundle enters).

The folding mechanism is provided roughly to the center of the saddle-stitching tray G and is formed of the folding plate 74, the folding rollers 81, and the conveying path H that conveys a folded sheet bundle. In FIG. 1, a reference numeral 326 denotes a home position sensor that detects the home position of the trailing-end tapping claw 251, and a reference numeral 323 denotes a folded-portion passage sensor that detects a center-folded sheet. A reference numeral 321 denotes a bundle detecting sensor that detects arrival of a sheet bundle at a center-folding position, and a reference numeral 322 denotes a movable trailing-end reference fence home position sensor that detects the home position of the movable trailing-end reference fence 73.

In the present embodiment, the lower tray 203 is provided with a detecting lever 501 that detects a stacking height of a center-folded sheet bundle PB in a manner swingable about a fulcrum 501 a. A sheet surface sensor 505 detects the angle of the detecting lever 501, thereby lifting up and down the lower tray 203 and detecting overflow.

FIGS. 6A and 6B to FIGS. 10A to 10B are views for explaining sheet conveying control performed by the staple unit and an operation performed by the blowing device. FIGS. 6A, 7A, 8A, 9A, and 10A are schematics of the edge binding tray F viewed from the front of the apparatus. FIGS. 6B, 7B, 8B, 9B, and 10B are schematics of the edge binding tray F viewed in a direction vertical to the edge binding tray F.

FIGS. 6A and 6B illustrate an operation performed when a first sheet is conveyed. The first sheet P1 passes through the conveying path D and reaches the pair of staple ejecting rollers 11. It is determined whether to blow air based on sheet information of the sheet P1. If it is determined to blow air, the blowing devices 54 a and 54 b starts to blow air. The blowing devices 54 a and 54 b are moved near the center of the sheet P1 according to the sheet size. Furthermore, the jogger fences 53 a and 53 b are moved to an optimum position in the width direction of the sheet P1 (direction orthogonal to the sheet conveying direction) according to the sheet size, thereby preparing for reception of the sheet. The tapping roller 12 is positioned at a retracted position not to prevent reception of the sheet.

FIGS. 7A and 7B illustrate a state in which the first sheet P1 is discharged onto the edge binding tray F by the pair of staple ejecting rollers 11. The sheet P1 discharged by the pair of staple ejecting rollers 11 is conveyed along the jogger fences 53 a and 53 b moving to a jogging operation start position. The blowing devices 54 a and 54 b blow air during the conveyance. The jogging operation start position is a position set in advance in the preparing operation.

As a result, an air space is formed between the sheet P1 and a sheet contacting surface of the edge binding tray F. This suppresses adhesion or cohesion of the sheet P1 to the contact (contacting) surface of the edge binding tray F, thereby preventing the sheet P1 from sticking thereto. While the first sheet P1 is being discharged by the pair of staple ejecting rollers 11, the second sheet P2 is conveyed through the conveying path D, which is illustrated in FIG. 7A.

FIGS. 8A and 8B illustrate a state in which conveyance of the first sheet P1 to the edge binding tray F is completed. As illustrated in FIGS. 8A and 8B, the sheet P1 is discharged onto the edge binding tray by the pair of staple ejecting rollers 11 while being blown by air output from the blowing devices 54 a and 54 b. This prevents the sheet P1 from sticking to the sheet contacting surface of the edge binding tray F. As a result, the sheet P1 is caused to drop to the trailing-end fence 51 by a tapping operation of the tapping roller 12 and its own weight. The second sheet P2 waits until the edge binding tray F is ready for receiving a subsequent sheet with the leading end of the second sheet P2 abutting on the nipping position of the pair of staple ejecting rollers 11.

FIGS. 9A and 9B illustrate a state in which the second sheet P2 is discharged onto the first sheet P1. While the second sheet P2 is being discharged onto the edge binding tray F by the pair of staple ejecting rollers 11, the blowing devices 54 a and 54 b blow air from the sides of the sheets P1 and P2. This operation forms an air space between the first sheet P1 and the second sheet P2, thereby suppressing or preventing adhesion therebetween. Preventing the first sheet P1 and the second sheet P2 from sticking to each other in this manner can suppress or prevent protrusion of the first sheet P1 or buckling of the second sheet P2.

FIGS. 10A and 10B illustrate a state in which discharge of a plurality of sheets onto the edge binding tray F is completed. FIGS. 10A and 10B illustrate a state of the sheet bundle PB aligned in the sheet conveying direction and the sheet width direction and stacked by repeating the operations illustrated in FIGS. 6A and 6B to FIGS. 9A to 9B. As described above, the sheets P are aligned in the conveying direction by the trailing-end reference fence 51 and in the sheet width direction by the jogger fences 53 a and 53 b. At this time, the blowing devices 54 a and 54 b provided to the jogger fences 53 a and 53 b, respectively, blow air. The air prevents the n-th sheet Pn discharged onto the edge binding tray F from sticking to the n−1-th sheet Pn−1 (n represents an integer equal to or larger than 2) previously discharged. Thus, the sheet bundle PB aligned with excellent alignment accuracy is formed on the edge binding tray F.

FIG. 11 is a block diagram of a control configuration of the image forming system formed of the sheet post-processing apparatus PD and the image forming apparatus PR. The sheet post-processing apparatus PD has a control circuit provided with a microcomputer including a CPU 101 and an input/output (I/O) interface 102, for example. The CPU 101 receives a signal supplied from a CPU of the image forming apparatus PR, each switch on an operation panel 105, or each sensor not illustrated, via a communication interface 103. The CPU 101 performs predetermined control based on the signal thus received. The CPU 101 causes a driver and a motor driver to control drive of solenoids and motors, respectively, and acquires sensor information in the apparatus via an interface. The CPU 101 causes the motor driver to control the drive of the motors via the I/O interface 102 depending on a control target and a sensor and acquires sensor information from the sensor. The control described above is performed by the CPU 101 reading a program code stored in a read-only memory (ROM), which is not illustrated, and loading the program code into a random access memory (RAM), which is not illustrated. The CPU 101 performs the control based on a computer program defined in the program code while using the RAM as a work area and a data buffer.

FIG. 12 is a flowchart of a process of blowing operation control according to the present embodiment. FIG. 13 is a front view of a selection screen 110 used for selecting a blowing mode on the operation panel 105 of the image forming apparatus PR. FIG. 14 is a front view of a setting screen 111 used for setting a blowing air volume.

If a blowing mode is selected, an automatic selection key 110 a, a forcible-ON key 110 b, and a forcible-OFF key 110 c are displayed on the selection screen 110 for the blowing mode as illustrated in FIG. 13. If a user touches the display area of one of the keys, the function thus touched is selected. If the user touches the automatic selection key 110 a to select automatic selection, setting is made such that a blowing device 400 automatically blows air in the case where coated paper is selected in setting of the sheet type. By selecting the forcible-ON key 110 b or the forcible-OFF key 110 c, the user can set whether to blow air regardless of the sheet type.

FIG. 14 illustrates an example display of the blowing air volume setting screen on the operation panel 105 of the image forming apparatus PR. The blowing air volume is automatically adjusted to an optimum blowing air volume for discharge based on sheet information (the sheet type, the sheet thickness, and the sheet size) received from the image forming apparatus PR. The blowing air volume setting screen 111 illustrated in FIG. 14 displays a state in which fan motor DUTY for driving the fan of the blowing device 400 is set to 70%. By touching a plus key 111 a or a minus key 111 b, the user can increase or decrease a default blowing air volume, thereby adjusting the blowing air volume.

In FIG. 12, if a blowing operation control is started, the selected state of the blowing mode is determined (Step S1). Which blowing mode is selected is determined based on the touch state on the selection screen 110 on the operation panel 105 of the image forming apparatus PR as illustrated in FIG. 13. If the user touches the automatic selection key 110 a, the system control waits until the edge binding tray F receives the sheet P (Step S2). Subsequently, sheet information is acquired from the image forming apparatus PR (Step S3). It is determined whether the sheet to be discharged is a piece of coated paper based on the sheet information thus acquired (Step S4).

If it is determined that the sheet is not a piece of coated paper, a blowing fan 411 is tuned OFF (Step S5). If it is determined that the sheet is a piece of coated paper, the blowing fan 411 is tuned ON (Step S6). Subsequently, the processing is terminated. The blowing air volume is automatically adjusted to an optimum blowing air volume for discharge based on the sheet information received from the image forming apparatus PR.

If it is determined that the forcible-OFF key 110 c is selected at Step S1, the blowing fan 411 is turned OFF (Step S5), and the processing is terminated. By contrast, if it is determined that the forcible-ON key 110 b is selected at Step S1, the blowing fan 411 is turned ON (Step S6), and the processing is terminated.

The processing of the flowchart illustrated in FIG. 12 is performed by the CPU 101.

As described above, controlling the timing and the volume of air blown from the blowing device 400 can suppress adhesion between the sheets. This can prevent buckling or sticking, thereby providing excellent alignment accuracy.

The present embodiment can provide the following advantageous effects.

1. The sheet processing apparatus includes a pair of staple ejecting rollers 11 that discharges a sheet P, an edge binding tray F that stacks thereon the sheet P discharged by the pair of staple ejecting rollers 11, blowing devices 54 a and 54 b that blow air to the sheet P, and jogger fences 53 a and 53 b that align the sheet P in a direction D2 orthogonal to a discharging direction D1 of the sheet P. With this configuration, an air space is formed on the lower surface side of the sheet P thus discharged. This makes it possible to prevent adhesion or sticking between the sheet P and the edge binding tray F and between the sheet Pn and the sheet Pn−1, which are sequentially discharged, and to align the sheets while maintaining this state. The alignment of the sheet P is ensured, whereby the sheet bundle PB is stacked with excellent alignment accuracy. Thus, in binding of the trailing end of the sheet bundle PB, no binding error occurs and the binding accuracy can be ensured.

2. The sheet processing apparatus changes the blowing air volume of the blowing devices 54 a and 54 b based on sheet information. This makes it possible to cause the blowing devices 54 a and 54 b to blow air to a piece of coated paper, which is likely to stick, and to blow no air to a piece of plain paper, which is unlikely to stick, for example. As a result, no unnecessary blowing operation is performed, thereby exerting energy-saving effects. Setting the air volume based on the type, the thickness, or the size of the sheet can prevent buckling or sticking, thereby providing excellent alignment accuracy.

3. The sheet processing apparatus can receive an input of the initial value of the blowing air volume through the selection screen 110 on the operation panel 105. This enables the user to set an appropriate air blowing volume besides automatic setting of the air blowing volume.

4. The sheet processing apparatus changes the blowing direction of the blowing devices 54 a and 54 b. This makes it possible to select a direction in which buckling or sticking can be prevented and excellent alignment accuracy can be provided in the blowing operation.

5. The sheet processing apparatus changes the blowing direction based on the sheet information. Thus, the blowing direction can be set based on the type, the thickness, or the size of the sheet.

6. The sheet processing apparatus moves the blowing ports 54 a 1 and 54 b 1 along the sheet discharging direction D1. This makes it possible to move the blowing ports 54 a 1 and 54 b 1 to a position where buckling or sticking can be prevented and excellent alignment accuracy can be provided in the blowing operation.

7. The sheet processing apparatus sets the position of the blowing ports 54 a 1 and 54 b 1 based on the sheet information. Thus, the position of the blowing ports 54 a 1 and 54 b 1 can be set based on the type, the thickness, or the size of the sheet.

8. The sheet processing apparatus causes the blowing devices 54 a and 54 b to start to blow air before the first sheet P1 discharged by the pair of staple ejecting rollers 11 comes into contact with the edge binding tray F. This can prevent sticking between the sheet P1 and the edge binding tray F and sticking between the sheet Pn, which is conveyed after the second sheet, and the sheet Pn−1, which is discharged just before the sheet Pn. As a result, the alignment of the sheet P is ensured, thereby providing excellent alignment accuracy of the sheet bundle PB.

The sheet disclosed in the claims corresponds to the sheets P, P1, P2, Pn−1, and Pn in the present embodiment. The discharging unit corresponds to the pair of staple ejecting rollers 11. The stacking unit corresponds to the edge binding tray F. The blowing unit corresponds to the blowing devices 54 a and 54 b. The aligning unit corresponds to the jogger fences 53 a and 53 b. The sheet processing apparatus corresponds to the sheet post-processing apparatus PD. The air blowing volume changing unit corresponds to the CPU 101. The operating unit corresponds to the operation panel 105. The wind direction changing unit corresponds to the CPU 101 and the angle changing mechanism of the louver, which is not illustrated. The blowing port corresponds to the blowing ports 54 a 1 and 54 b 1. The moving unit corresponds to the moving mechanism, which is not illustrated. The image forming system corresponds to the system including the sheet post-processing apparatus PD and the image forming apparatus PR. The CPU 101 sets the position of the blowing port and changes the blowing direction based on the sheet information. The CPU 101 starts a blowing operation before the first sheet comes into contact with the edge binding tray F.

The present invention can prevent sheets from sticking and ensure excellent alignment accuracy.

Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth. 

What is claimed is:
 1. A sheet processing apparatus for receiving and processing a sheet conveyed from an image forming apparatus, the sheet processing apparatus comprising: a discharging unit configured to discharge the sheet; a stacking unit configured to stack thereon the sheet discharged by the discharging unit; a blowing air unit configured to blow air along a direction parallel to a surface of the sheet being stacked; a first alignment unit having a pair of alignment plane opposed each other, the first alignment unit configured to align the sheet in a direction parallel to a discharging direction of the sheet; and a second alignment unit configured to align the sheet in a direction orthogonal to the discharging direction of the sheet, wherein the blowing air unit is provided at a position opposed to the alignment plane.
 2. The sheet processing apparatus set forth in claim 1 further comprising a blowing air flow rate changing unit configured to receive sheet information from the image forming apparatus and change the blowing air flow rate based on the sheet information.
 3. The sheet processing apparatus set forth in claim 1 further comprising an initial value input unit configured to manually input an initial value of the blowing air flow rate.
 4. The sheet processing apparatus set forth in claim 1 further comprising a wind direction changing unit configured to change a blowing direction of the blowing air unit.
 5. The sheet processing apparatus set forth in claim 4, wherein the wind direction changing unit receives sheet information from the image forming apparatus and changes the blowing direction based on the sheet information.
 6. The sheet processing apparatus set forth in claim 1 further comprising a moving unit configured to move the blowing air unit along the discharging direction of the sheet.
 7. The sheet processing apparatus set forth in claim 6, wherein the moving unit receives sheet information from the image forming apparatus and moves the blowing air unit based on the sheet information.
 8. The sheet processing apparatus set forth in claim 1, wherein the blowing unit starts to blow air before a moment when a first sheet discharged by the discharging unit contacts with the stacking unit.
 9. An image forming system comprising: the sheet processing apparatus set forth in claim 1; and the image forming apparatus.
 10. A method for using the sheet processing apparatus set forth in claim 1, comprising: by the discharging unit, discharging the sheet; by the stacking unit, stacking thereon the sheet discharged by the discharging unit; by the blowing air unit, blowing air along the direction parallel to the surface of the sheet being stacked; by the first alignment unit having a pair of alignment plane opposed each other, the first alignment unit configured to align the sheet in a direction parallel to a discharging direction of the sheet; and a second alignment unit configured to align the sheet in a direction orthogonal to the discharging direction of the sheet, wherein the blowing unit is provided at a position opposed to the alignment plane. 